M. K. Wegener

Validation of multicriteria analysis models

Validation procedures play an important role in establishing the credibility of models, improving their relevance and acceptability. This article reviews the testing of models relevant to environmental and natural resource management with particular emphasis on models used in multicriteria analysis (MCA). Validation efforts for a model used in a MCA catchment management study in North Queensland, Australia, are presented. Determination of face validity is found to be a useful approach in evaluating this model, and sensitivity analysis is useful in checking the stability of the model

Factors affecting cane yield and commercial cane sugar in the Tully district

The Tully Sugar Mill has collected information about sugarcane supplied for crushing from every block in the mill district from 1970 to 1999. Data from 1988 to 1999 were analysed to understand the extent of the variation in cane yield per hectare and commercial cane sugar in the Tully mill area. The key factors influencing the variation in cane yield and commercial cane sugar in this commercial environment were identified and the variance components computed using a restricted maximum likelihood methodology. Cane yield was predominantly influenced by the year in which it was harvested, the month when the crop was ratooned (month of harvest in the previous year) and the farm of origin. These variables were relatively more important than variety, age of crop or crop class (plant crop, first ratoon through to fourth or older ratoons) and fallowing practice (fallow or ploughout-replant). The month-of-ratooning effect was relatively stable from year-to-year. Commercial cane sugar was influenced by the year of harvest, the month of harvest and their interaction, in that the influence of the month of harvest varied from year to year. Variety and farm differences were also significant but accounted for a much lower portion of the variation in commercial cane sugar. An empirical model was constructed from the key factors that influenced commercial cane sugar and cane yield to quantify their combined influence on sugar yield (t/ha). This may be used to assist mill personnel to predict their activities more accurately, for example to calculate the impact of a late finish to the current harvest season on the following years crop.

Commercial cane sugar trends in the Tully sugar district

Commercial cane sugar (CCS), as measured by sugar mills, is in decline in the wet tropics of Australia. One of these mills, Tully Sugar Ltd, has measured CCS in the factory as required by legislation and also measured whole clean stalk CCS through a small mill, which is free of contaminants. ‘Factory CCS’ measures the CCS of cane entering the mill, after it has been harvested. The harvesting and transport process delivers to the mill cane that is contaminated by extraneous matter such as leaf material and soil. Beween 1988 and 1998, 1516 blocks were sampled for ‘small mill CCS’. These data were combined with block productivity information to determine the trends in small mill CCS and factory CCS using a linear mixed model analysis as the data were unbalanced. Other data, including the date of harvest for factory CCS, date of sampling for small mill CCS, farm of origin and cane variety were available and fitted as random effects in the mixed model. Year was fixed to determine time related trends in the 2 measures of CCS. Small mill CCS was higher than factory CCS and remained constant from 1988 to 1998. Predicted factory CCS declined from 12.76 units in 1988 to 10.91 units in 1998. We conclude that the CCS levels in whole clean stalks were actually stable, since small mill CCS remained constant over the 10-year period. Possible reasons for the differences in the trends for the 2 CCS measures are discussed.

The evaluation of the spatial and temporal stability of sugarcane farm performance based on yield and commercial cane sugar

In broader catchment scale investigations, there is a need to understand and ultimately exploit the spatial variation of agricultural crops for an improved economic return. In many instances, this spatial variation is temporally unstable and may be different for various crop attributes and crop species. In the Australian sugar industry, the opportunity arose to evaluate the performance of 231 farms in the Tully Mill area in far north Queensland using production information on cane yield (t/ha) and CCS (a fresh weight measure of sucrose content in the cane) accumulated over a 12-year period. Such an arrangement of data can be expressed as a 3-way array where a farm × attribute × year matrix can be evaluated and interactions considered. Two multivariate techniques, the 3-way mixture method of clustering and the 3-mode principal component analysis, were employed to identify meaningful relationships between farms that performed similarly for both cane yield and CCS. In this context, farm has a spatial component and the aim of this analysis was to determine if systematic patterns in farm performance expressed by cane yield and CCS persisted over time. There was no spatial relationship between cane yield and CCS. However, the analysis revealed that the relationship between farms was remarkably stable from one year to the next for both attributes and there was some spatial aggregation of farm performance in parts of the mill area. This finding is important, since temporally consistent spatial variation may be exploited to improve regional production. Alternatively, the putative causes of the spatial variation may be explored to enhance the understanding of sugarcane production in the wet tropics of Australia.

Mechanization technology: The key to sugarcane production in China

Sugarcane is an important cash crop in southern China now planted on about 1.5 million ha in the main production areas in Guangxi, Zhuang Autonomous Region and Yunnan, Guangdong, and Hainan Provinces. Since the cost of labor in China is increasing rapidly and the price of local sugar is uncompetitive with the product from mechanized international producers, China needs to change its sugarcane production methods from manual work to mechanization in order to catch up with international trends in this global industry. Although a lot of effort in China have gone into sugarcane mechanization since the 1960s, the overall level of mechanization in sugarcane production is still only approximately 30%, which is about 20% lower than that achieved in the other main field crops. Almost all of the sugarcane grown in China is still harvested by hand. In order to summarize past experience and promote the mechanization of sugarcane production in China, this paper reviews the whole process of developing mechanization since 1960s and describes the current state of sugarcane mechanization in China. The research currently being undertaken and the main obstacles to be overcome in developing a mechanized sugarcane production system, are described. The design and testing of sugarcane harvesting machinery and its key components has been a significant research area by some Chinese universities, research institutes, and manufacturing companies in these past decades. This paper reviews that research and outlines the main achievements which have been made in this area. Mechanized harvesting systems for sugarcane, and the appropriate harvesting patterns suitable for different growing conditions applying in China, have also been studied. The paper concludes with some comments on the future directions for progress in China

Rain Damage on Three Strawberry Cultivars Grown in Subtropical Queensland

In Queensland, Australia, strawberry (Fragaria × ananassa Duchesne) is grown in open fields and rainfall events can damage fruit. Following a rain event, damage was evaluated on three commercial cultivars. ‘Rubygem’ (80%) had more fruit damaged than ‘Strawberry Festival’ (55%) and ‘Camarosa’ (61%). “Etch,” where the surface of the fruit is eroded and, consequently, the seeds are raised relative to the damaged surface, was the most frequently occurring (>80%) damage type and was distributed on the body and tip of the fruit, while some fruit (<16%) showed cracking. Fully mature fruit was damaged (>80%) more than partially mature fruit, which differed between ‘Strawberry Festival’ (16%) and ‘Rubygem’ (68%). Cultivars that are resistant to rain damage would reduce losses and lower risk for the growers.

The use of crop yield prediction as a tool for land evaluation studies in Northern Australia

Adequate prediction of crop yield is essential in quantitative land evaluation studies. The AUSCANE simulation model, local expert opinion and historical records were used to predict crop yield and ccs (a measure of sugar content in the cane stalk) for sugarcane production for land mapping units at two different scales of investigation in the Herbert River district of northern Australia. Simulations were undertaken for a period of 25 years. The model performed adequately on clay soil types; however, it generally overestimated yield and ccs values on sandy soil types and underestimated values on loamy soil types. Yield estimates were influenced by mean daily solar radiation and changes in the soil water balance. Results from the yield prediction process have played a significant role in the development of a tripartite system of land evaluation based on crop yield prediction, expert systems for biophysical and economic land suitability and risk analysis.

An evolutionary economic perspective on technical change and adjustment in cane harvesting systems in the Australian sugar industry

Australian sugar-producing regions have differed in terms of the extent and rate of incorporation of new technology into harvesting systems. The Mackay sugar industry has lagged behind most other sugar-producing regions in this regard. The reasons for this are addressed by invoking an evolutionary economics perspective. The development of harvesting systems, and the role of technology in shaping them, is mapped and interpreted using the concept of path dependency. Key events in the evolution of harvesting systems are identified, which show how the past has shaped the regional development of harvesting systems. From an evolutionary economics perspective, the outcomes observed are the end result of a specific history.

Industry Structure and the Reform of the Queensland Sugar Industry: A Computational Model

A computational model of pricing and profitability in the Queensland sugar industry is applied to a comparative analysis of likely alternative industry structures that may arise in the wake of industry reform. Implementation of proposals suggested by the sugar industry review working party and in some of the submissions to it are also examined. The model is a simple static optimisation model of the trade in sugarcane in a local mill area. Numerical results are presented to compare prices and profitability for both a representative mill and growers in a monopsony situation, a contestable market, and under the current institutional arrangement. The results indicate that although deregulation has the potential to lead to improved welfare for both growers and the mills, this will only be the case if mills price competitively, i.e. in the contestable market case where the threat of competition from neighbouring and competing mills is sufficient to force the incumbent mill to pay for cane at a competitive price to prevent the entry of potential competitors.

Indonesian Sugar Production and Recommendations for Industry Recovery

The history of the Indonesian sugar economy reveals a gloomy story of decline from being one of the largest exporters to the world’s biggest sugar importer. The suspected reasons for that reversal of status are that sugar production practices have not kept up with prominent international producers such as Australia, Brazil, and Thailand. The yield of Indonesian sugarcane is apparently reasonable, even higher than that achieved in Thailand as the second largest sugar exporter, but harvesting techniques, time of harvesting, and the mills’ processing efficiency need to be improved. Furthermore, irrigation development and greater attention to fertilization could lead to improvements in both yield and cane quality, while better transportation systems could reduce sugar losses between harvesting and processing. After discussing the causes of the Indonesian sugar industry’s failure to grow, the paper presents several recommendations to introduce better varieties of cane as a priority, through researcher and development. This might be achieved through collaboration with international sugarcane research centers such as strengthening existing links with Sugar Research Australia to support the development of better cane varieties and tackle disease issues. Such collaboration can be built through a bilateral agreement with terms and conditions agreed by both parties. Better harvesting techniques, including an assessment of the transition to mechanized harvesting, are required, something the government has already instructed. Furthermore, the number of sugar mills in the industry must be reduced, especially those old mills and can’t be revitalized easily. Better fertilizing strategies and better access to irrigation are needed to achieve increased productivity from cane growing land and it could be helpful to introduce rules to deliver sugarcane to nearby mills. If all of these issues can be addressed, and if the factors that led to the decline in the Indonesian sugar industry can be corrected, the prosperity of the sugar industry in Indonesia should be recovered.